1. Field of the Invention
The present invention relates to a label printer which is widely used, especially in POS, FA, physical distribution, etc., and more particularly to a label printer utilizing an ink jet print system.
2. Related Background Art
Hitherto, none of the label printers using the ink jet printing method have been put to practical use. The advantages of the typical ink jet recording may include excellent quietness owing to out-of-contact with the print medium, high printing rate, printing with high density, easy color constitution, and small size. On the other hand, most label printers take the form of conveying a so-called label sheet having a number of labels bonded in succession on a length of the release sheet referred to as a separator and formed into a roll, in which in applying the ink jet system to the label printer, some measures must be taken to suppress the floating or skew running of the sheet in the printer head portion.
In recent years, the bar code is liable to be insufficient, the color constitution is examined, and from this regard, the adoption of the ink jet system is effective, but if an the printing speed of the label printer is attempted in designing the color label printer, the frequency of the print signal to be given to the print head of each color is increased, which requires the capacity of drive power source to be increased, resulting in larger size of the power source and causing the increase of the cost.
Further, in the case of the ink jet system, to prevent the unstable discharge of the ink because of being left unused for the long term, it is effective to use a so-called recovery system to circulate the ink around the print head. This recovery operation is typically performed with a recovery unit referred to as a recovery system placed in direct contact with the print head which is printing means. However, as the label printer typically utilizes the label sheet wound like a roll, the sheet never disappears at the print position. Accordingly, the disposition of the recovery system and the design of the recovery sequence are very difficult, as compared with those intended for the cut sheet such as the normal office printer.
Along with these, it is very difficult to make compact the print head, the recovery system unit, the ink supply system, and the printing medium conveyance system.
Several normal label printers have been put to practical use, which adopt a thermal transfer recording method of transferring the ink onto the recording medium via the ink ribbon using the heat generating elements, or a thermal recording method of coloring the thermosensible recording sheet by heating.
At present, among the ink jet recording systems using the heat generating elements, there is a bubble jet system (thermal ink jet system) discharging the ink by producing bubbles in the liquid ink due to the heat energy generated by the heat generating elements, and using the pressure generated upon the growth of the bubbles, which is applied to the output devices (printers) in many fields.
The durability of the print head using the above heat generating elements may be governed by the disconnection of a resistor useful as the heat generator, the failure of a switching element such as a transistor for controlling the conduction to each heat generator, and so on. Further, it may be also governed by the damage of the head due to the friction caused by its contact with the paper or ink ribbon in the print heads of contact type, particularly, for the thermal recording or thermal transfer recording, or the clogging with the ink or contamination in the ink flow passage near the heat generating circuit in the ink jet recording system.
When part of the heat generating elements of the print head, in other words, the print segment, is broken by above factors, the information to be printed may be partially lacked, or the printed information may be recognized incorrectly, whereupon the replacement of the print head is required. However, the print head is an expensive element, while the labor for the replacement and the inoperative loss time required for the replacement may occur, thereby giving rise to the increase in the print cost.
To cover the above drawbacks, a proposal has been made as disclosed in Japanese Laid-Open Patent Application No. 61-104872, in which the electric current too small to effect printing is passed through the heat generating circuit of the print head to detect the disconnected portion, determining whether or not print data is present at the print position corresponding to its disconnected portion, in which if not present, the printing is directly made, or otherwise, the location without print data is searched in its neighborhood, and if such a location is present, the printing is made at that location. Or a method of representing the life of the thermal head as the recordable length, with an indication "THE DURABILITY OF THIS THERMAL HEAD IS ROUGHLY 50KM" has been taken to indicate the replacement time.
On the other hand, in conventional printers, because if the printing is performed irrespective of the amount of the serpentine or skew running of the print medium to be printed, the print quality may be degraded or the color aberration may occur in the color printer, the amount of serpentine or skew running is detected, and in excess of the set amount of serpentine or skew running, the operation is stopped as an abnormal conveyance, with an error indication on the screen to prompt the operator to reset or reinsert of the sheet.
However, regarding the life of the head, owing to the ruled line or frame contained in the print context, the number of conductions to a specific heat generating circuit within the print head increases, upon printing a number of sheets, so that the life of the heat generating circuit will determine the life of the whole of the print head, or even if the printing is performed by shifting the disconnected portion, the number of conductions to the specific heat generating circuit also increases, possibly resulting in a risk of causing a disconnection of the line.
Also, regarding the skew or serpentine running of the printing medium, the operation is stopped if the amount of skew or serpentine running is in excess of a certain value, and in the constitution of having the error indication, the set value for satisfying the print quality is smaller as the print context is more highly defined, resulting in a problem that if there occurs even a slight amount of skew or serpentine running, the printing is stopped due to the error detection, frequently necessitating the error release operation, or causing the useless consumption of the print medium.
The present invention has paid attention to specific problems with the label printer for performing the printing on the labels bonded on the release paper.
In the printer with the labels bonded in succession on the release paper as the printing medium, the labels of various shapes are selected in accordance with the print format or the quantity of information to be printed, and mounted on the printer. If the shape of the labels mounted does not accord with the print format, the printing may occur out of the label portion, resulting in the problem of contaminating the conveyance system, degrading the print quality, or shortening the life of the printer. Therefore, it is preferable to judge the shape of the labels inside the printer. A device for judging the shape of such labels has been described in, for example, Japanese Laid-Open Patent Application No. 58-194584. That is, the length of label in a lateral direction regulates one side of each of successive labels, in which a required number of detectors are disposed along a width direction near the other side to determine the length in the lateral direction in accordance with the signals from such detectors. The length of label in a longitudinal direction can be determined by a method of providing apertures indicating the print start in the labels to obtain the distance from the first aperture to the next aperture by counting the number of pulses for a sheet feed motor, calculating the length of label from the counted value, and judging whether or not the label length accords with the print format.
However, the above conventional technique is effective if the shape of the label is rectangular, but when the label of other shape is mounted, no consideration is taken and the following problems were encountered.
(1) The rectangular shape of label can be only judged, and when the shape of label is changed, for example, when the label of circular, elliptic, or lozenged shape is mounted on the printer, it can not be judged. As the label is mostly used for the appeal of the product, a variety of shapes are used. Therefore, the judgment only for the rectangle is insufficient.
(2) It is difficult to judge whether or not the context printed on the label coincides with the information to be printed. Particularly when the bar code is printed, the judgment can not be made if the bar is not printed due to some cause, or the print density is lower. If the bar code data is not printed correctly, the system will process false information, and it is quite important to secure correct printing in the printer.
Also, in the conventional printers, in printing on the continuous paper like a roll such as the label sheet, the print process is constituted of a developing process of data for one page and a printing process for one page which is started after development, and when printing data exceeding the length of used label over a plurality of labels, the printing may occur on the mount between labels, resulting in a problem that the regularity of data can not be held by a combination of labels which are then pasted.
Similarly, in printing the printed matter formed of a group of multiple pages onto the continuous paper, the page designation is cumbersome when the printing is retried due to jam, and is quite inconvenient to the operation. Also, the disposition or reprint of page units is required to secure the validity of the printed matter, presenting a significant problem on the management.
Further, in the conventional printers, print data is developed in the area of one page by designating the relative or absolute position, whereas when print data is developed by designating the relative position, the positional deviation of other print data may occur owing to redundant print data such as character information, or when print data is developed by designating the absolute position, print data areas may overlap each other in designation, which was quite inconvenient on the design of document and the creation of print data.
The peculiar problems with the label printer may include:
Insufficient detecting ability concerning various label shapes PA1 Inability of confirming whether or not the bar code has been correctly formed PA1 Difficulty in forming data over multiple labels by dividing it PA1 Difficulty in reprinting data upon divided formation PA1 Inconvenience in making the format of print data PA1 Insufficient detecting ability concerning various label shapes PA1 Inability of confirming whether or not the bar code has been correctly formed PA1 Difficulty in forming said over. multiple labels by dividing it PA1 Difficulty in reprinting data upon divided formation PA1 Inconvenience in making the format of print data
In performing the image output for the information desired by the operator using the printer, it is desired in some cases to add some information, besides that information concerned. For example, in the applications of printing product information including the bar code to the labels, using a plurality of label printers, and pasting them to the products, it is quite convenient that printer information is additionally provided, besides the product information, because the printer which has printed can be immediately discriminated, if a print failure happens, thereby enabling the rapid measure such as a maintenance to be taken.
Also, such labels are bonded in succession on the release paper and formed into a roll in most cases, wherein a number of labels are printed successively beforehand with this roll mounted on the printer, and pasted on the product separately. And when there are a plurality of different types of products, a plurality of different types of labels correspondingly are printed beforehand, whereas if it can be seen at a glance where the print context is changed in pasting the label onto the product as the product information has similar format, no false pasting will occur, and no burden is imposed on the operator.
In the conventional printers, in adding the specific information, it is obliged to add the specific information to the information to be originally printed, which was cumbersome. Also, as above described, where the change of print context occurs in printing the labels in succession, a constitution has been disclosed in Japanese Laid-Open Patent Application No. 62-10852, in which on one label between a group of labels printed previously and a group of labels to be printed later, the character information indicating the previously printed context or the later printed context is only printed, although the character information itself must be created by the operator himself, and the label having that information printed is not subjected to other uses than clarifying that the change has occurred, and wastefully used.
Also, in recent years, as the method of coding the information to be used, various types of bar codes have been put to practical use. Since the bar code is used for the physical distribution or management, read by an equipment referred to as a reader, and easily converted into data which can be processed on the computer, the symbols are standardized for each application, and employed in many fields. More recently, even in the system of the printer of personal use or host apparatus, it can be output. Also, in the label printer, the bar code may be often used to record the information of the object to paste the label sheet.
However, the bar code is required to print the information quite correctly, owing to its features, and be presented for particular purposes in reliable manner.
The bar code symbol in accordance with various standards such as JAN, UPC, EAN, etc., can represent each number of 0 to 9 (character) by a combination of the black bar and the white bar satisfying the breadth of a certain standard.
For example, in Japan, JAN (Japanese Article Number) code has been established as the unique bar code symbol of Japan. JAN code is one in which the character is represented by a combination of two black bars and two white bars. This is defined in more detail in JISX0501, wherein the strict accuracy is required, such that when the magnification is one, the module dimension is 0.33 mm, with the bar width tolerance being .+-.0.101 mm, and when the magnification is 0.8 at minimum, the module dimension is 0.264 mm, with the bar width tolerance being .+-.0.035 mm.
The apparatus for printing such bar code was conventionally an apparatus having the thermal head in most uses, but it is considerably difficult to make the adjustment of dot system (or width) because of its constitution of controlling the heating value of the heat generator by changing the applied voltage or application time.
Particularly, in recording the bar code using the thermal heat, the heat accumulation in the specific heat generating elements is problematical because specific heat generating elements are driven consecutively when printing the bar extending in a direction (sheet conveying direction) orthogonal to the line head. In particular, because the upper portion of the bar to be printed later in a direction of the bar height, is formed thicker than the lower portion due to accumulated heat in the heat generating element, there is the necessity for controlling the energy to be applied to the heat generating element.
On the other hand, in printing in the direction other than the conveyance direction, such as the direction of line head, a number of heat generating elements disposed in succession in the direction of the array of heat generating elements of the full-multi head are driven at a time, and due to the accumulated heat, the elements not relating to printing may be heated, producing streaks in the tailing state to affect the image quality. Particularly, in the bar code with higher printing accuracy, the bar interval having no printing may be disordered, adversely effecting the detection accuracy of the bar code to great extent.
Also, if recording in the low temperature state of the heat generating elements (after succession of unprinted lines), the coloration is not fully made, and there is a risk that the fine line may be recorded at lower density, so that it can not be correctly detected by a bar code scanner.
Therefore, the control is required to effect full coloration at the next recording in the elements not involving recording, or to prevent excessive temperature elevation of the heat generating elements in the elements involving successive recording.
Thus, the apparatus constitution having the head with the ink jet system is effective to adopt. However, the ink jet head effects the printing on the printing medium by discharging the ink through discharge ports, in which there may occur a deviation (hereinafter referred to as "offset") between the ideal impinging position of the discharged ink and the actual impinging position of the ink, but in the constitution where the distance between the head and the platen in printing is fixed, the line width due to the offset becomes unstable, when the distance (head gap) between the discharge port and the printing medium is changed by the thickness of the printing medium to be conveyed on the platen, or when the fine bar is printed, resulting in a risk that a required bar accuracy can not be retained.
Regarding all printers of the type of effecting the image formation of dots, such as a thermal printer, the black bar may be broadened at both ends because of the area of formed dot, in which there is a risk that the black bar is thicker than the regular width. Along with this, the white bar provided between black bars may be thinner.